My Ferritin levels are high at 283, vitamin D low at 17. No hemochromatosis. Undiagnosed autoimmune. Possible causes? Are these related medically?

Not related. Deficiency of vitamin D is very common. You can easily address that by taking vitamin D3 supplement at a dose of about 5000 units/day for three months. After that you may take abut 2000 units/day.